Idk what to do

So, I didn't really know where to write this, i just need some help. For last 2 months or so, ive been having thoughts about leaving my boyfriend of 2 years. Like, i mean DAILY. sometimes it even feels more like fantasizing about it. I dont think i can bring myself to actually do it, for a few reasons, but i dont know what im supposed to do, i dont know if im happy with him anymore... theres also something else that has only just came up that makes it even more complicated but thats a whole other story... i havent spoken to my boyfriend about it because he'd lose his shit. I dont know what kind of advice im looking for so anything will do